1. Field of the Invention
The present invention is in the field of cured tire treads for retreading tires.
2. Description of the Related Art
When tires become worn, they can be restored with new tread. In the cold recapping process, a cured rubber tread band with a tread pattern already impressed in its outer surface is attached to a tire carcass, often with a cushion gum layer between the tread band and the tire carcass. The tire is then placed in an autoclave, and heated under pressure for an appropriate time to induce curing of the gum layer, and binding of the gum layer to the inner or sole side of the tread layer and the carcass. The term “cure” refers to the formation of cross-links between the elastomer molecules in the rubber compound.
In order to improve the bonding of the cured tread layer to the carcass, the sole side surface of the cured tread layer may be textured. One known texturing process uses a brush or grinding wheel to impart to the rubber surface a roughness that is suitable for the subsequent bonding. An additional benefit of the texturing process is that it removes any mold release agents from the surface of the rubber. The mold release agents typically include silicone which has an adverse effect on the bonding of the sole side surface of the tread band.
A schematic view of a prior art texturing process is shown in FIG. 1. A tread band 20 is positioned between a series of support rollers 30 and abrasive rollers 40. The support rollers 30 engage the top surface 22 of the tread side 24 of the tread band 20 while the abrasive rollers 40 engage the sole side surface 26 of the tread band 20. The abrasive rollers 40 are being pushed downward on the tread band 20 while the abrasive rollers 40 rotate to impart a texturing or roughening to the sole side surface 26 of the tread band 20. A problem with this prior art method becomes apparent when using this process on tread bands 20 having wide and/or deep grooves 28. An example of tread band 20 having such a tread pattern is shown in FIG. 2. When a tread band 20 having tread patterns exhibiting wide and/or deep grooves 28 is roughened according to the process shown in FIG. 1, the grooves 28 are unsupported by the support rollers 30. The lack of support allows the sole side surface 26 of the tread band 20 to deflect away from the abrasive rollers 40. This may result in unroughened areas 32 of the sole side surface 26 opposite the grooves 28 of the tread side 24 of the tread band 20 as best shown in FIG. 3.